Multi-layered core golf ball

ABSTRACT

The present invention is directed towards a multi-layered core golf ball that comprises a center, a cover and a thin laminate comprising of at least one core layer formed around the center to create an inner ball, wherein the laminate includes at least one outer core layer that is relatively stiff and hard relative to the center, at least one outermost core layer that is heavily filled with a density increasing material and at least one core layer that functions as a moisture vapor barrier. One core layer may serve to provide all the functions in a single layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/948,692, filed Sep. 10, 2001, which is acontinuation-in-part of U.S. patent application Ser. 09/172,608, filedOct. 18, 1998, now U.S. Pat. No. 6,302,808, which is a division of U.S.patent application Ser. No. 08/943,932, filed Oct. 3, 1997, now U.S.Pat. No. 6,056,842, also a continuation-in-part of U.S. application Ser.No. 08,996,718, filed Dec. 23, 1997, now U.S. Pat. No. 6,124,389, whichis a continuation-in-part of U.S. application Ser. No. 08/746,362, filedNov. 8, 1996, now U.S. Pat. No 5,810,678, which is acontinuation-in-part of U.S. patent application Ser. No. 08/706,008,filed Aug. 30, 1996, now U.S. Pat. No. 5,813,923, which is acontinuation-in-part of U.S. patent application Ser. No. 08/603,057,filed Feb. 16, 1996, now U.S. Pat. No. 5,759,676, which is acontinuation-in-part of U.S. patent application Ser. No. 08/482,522,filed Jun. 7, 1995, now U.S. Pat. No. 5,688,191 also acontinuation-in-part of U.S. patent application Ser. No. 09/630,387,filed Aug. 1, 2000, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/603,057, filed Feb. 16, 1996, now U.S. Pat. No.5,759,676; also the application is a continuation-in-part of U.S. patentapplication Ser. No. 09/815,753, filed Mar. 23, 2001, the disclosures ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention is directed to improved golf balls and,specifically to golf balls comprised of multi-layer cores. Moreparticularly, to where the outer core layers are thin laminate layers ofspecific hardness and densities.

Generally, golf balls have been classified as wound balls or solidballs. Wound balls are generally constructed from a liquid or solidcenter surrounded by tensioned elastomeric material. Wound balls aregenerally thought of as performance golf balls and have a goodresiliency, spin characteristics and feel when struck by a golf club.However, wound balls are generally difficult to manufacture whencompared to solid golf balls.

Early solid golf balls were generally two piece balls, i.e., comprisinga core and a cover. More recently developed solid balls are comprised ofa core, a mantle layer and a cover, in order to improve the playingcharacteristics of the ball.

The prior art is comprised of a variety of golf balls that have beendesigned to provide particular playing characteristics. Thesecharacteristics are generally the initial velocity and spin of the golfball, which can be optimized for various types of players. For instance,certain players prefer a ball that has a high spin rate in order tocontrol and stop the golf ball. Other players prefer a ball that has alow spin rate and high resiliency to maximize distance. Generally, agolf ball having a hard core and a soft cover will have a high spinrate. Conversely, a golf ball having a hard cover and a soft core willhave a low spin rate. Golf balls having a hard core and a hard covergenerally have very high resiliency for distance, but are hard feelingand difficult to control around the greens. Various prior art referenceshave been directed to adding a mantle layer or second cover layer toimprove the playability of solid golf balls.

The spin rate of golf balls is the end result of many variables, one ofwhich is the distribution of the density or specific gravity within theball. Spin rate is an important characteristic of golf balls for bothskilled and recreational golfers. High spin rate allows the more skilledplayers, such as PGA professionals and low handicapped players, tomaximize control of the golf ball. A high spin rate golf ball isadvantageous for an approach shot to the green. The ability to produceand control backspin to stop the ball on the green and side spin to drawor fade the ball substantially improves the player's control over theball. Hence, the more skilled players generally prefer a golf ball thatexhibits high spin rate.

On the other hand, recreational players who cannot intentionally controlthe spin of the ball generally do not prefer a high spin rate golf ball.For these players, slicing and hooking are the more immediate obstacles.When a club head strikes a ball, an unintentional side spin is oftenimparted to the ball, which sends the ball off its intended course. Theside spin reduces the player's control over the ball, as well as thedistance the ball will travel. A golf ball that spins less tends not todrift off-line erratically if the shot is not hit squarely off the clubface. The low spin ball will not cure the hook or the slice, but thelower spin will reduce the adverse effects of the side spin. Hence,recreational players prefer a golf ball that exhibits low spin rate.

Reallocating the density or specific gravity of the various layers ormantles in the ball is an important means of controlling the spin rateof golf balls. In some instances, the weight from the outer portions ofthe ball is redistributed to the center of the ball to decrease themoment of inertia thereby increasing the spin rate. For example, U.S.Pat. No. 4,625,964 discloses a golf ball with a reduced moment ofinertia having a core with specific gravity of at least 1.50 and adiameter of less than 32 mm and an intermediate layer of lower specificgravity between the core and the cover. U.S. Pat. No. 5,104,126discloses a ball with a dense inner core having a specific gravity of atleast 1.25 encapsulated by a lower density syntactic foam composition.U.S. Pat. No. 5,048,838 discloses another golf ball with a dense innercore having a diameter in the range of 15-25 mm with a specific gravityof 1.2 to 4.0 and an outer layer with a specific gravity of 0.1 to 3.0less than the specific gravity of the inner core. U.S. Pat. No.5,482,285 discloses another golf ball with reduced moment of inertia byreducing the specific gravity of an outer core to 0.2 to 1.0.

In other instances, the weight from the inner portion of the ball isredistributed outward to increase the moment of inertia therebydecreasing the spin rate. U.S. Pat. No. 6,120,393 discloses a golf ballwith a hollow inner core with one or more resilient outer layers,thereby giving the ball a soft core, and a hard cover. U.S. Pat. No.6,142,887 discloses an increased moment of inertia golf ball comprisingone or more mantle layers made from metals, ceramic or compositematerials, and a polymeric spherical substrate disposed inwardly fromthe mantle layers.

These and other references disclose specific examples of high and lowspin rate ball with ranges of specific gravity, ranges of diameter forthe core and ranges of thickness for the outer layers, etc. They,however, do not offer any universal guidelines to control the spin rateof golf balls. Hence, there remains a need in the art for an improvedgolf ball with controlled spin rates.

Other prior art golf balls have multiple core layers to provide desiredplaying characteristics. For example, U.S. Pat. No. 5,184,828 claims toprovide a golf ball having two core layers configured to providesuperior rebound characteristics and carry distance, while maintainingadequate spin rate. More particularly, the patent teaches an inner coreand an outer layer and controlling the hardness distribution in theouter layer and in the inner core in such a way that the golf ball has amaximum hardness at the outer site of the inner core. The patent allegesthat such a distribution of hardness in the core assembly allows highenergy to accumulate at the interface region where the hardness is at amaximum. The patent further claims that the energy of the club face isefficiently delivered to the maximum hardness region and transferredtoward the inner core, resulting in a high rebound coefficient. However,since golf balls having hard cores and soft covers provide the mostspin, the distribution taught by this patent would result in maximumcore hardness at the interface when hit by a driver. Therein the ballhas a relatively high driver spin rate and not very good distance. Sincethe ball in this patent has a softer outer core layer, the ball shouldhave a lower spin rate for shorter shots such as an eight iron, wherespin is more desirable. Thus, the ball taught by this patent appears tohave many disadvantages.

In order to improve the playing characteristics of a solid golf ball,Kasco, Inc. provided a ball called Rockets™. The Rockets™ ball iscomprised of a center, two layers and a cover. The center and the twolayers are all comprised of polybutadiene rubbers.

In particular, tests on such balls have shown that golf balls arecomprised of a center having a diameter of about 1.0 inch, a first layerhaving an average thickness of about 0.125 inch and a second layerhaving an average thickness of about 0.13 inch. The center has a Shore Chardness of about 59 at the center and 60 at the center mid pointbetween the core center and the outer surface of the center. The firstlayer has a Shore C hardness of about 61, and the second layer has aShore C hardness of about 73. The cover of the Rockets™ golf balls areharder than 65 Shore D and the compression is about 88.

Based upon the parting lines at each layer, it appears that Kascomanufactures the Rockets™ golf ball core by forming the center,compression molding the first layer around the center and compressionmolding the second layer onto the center and first layer. It appearsthat the cover is molded using a retractable pin injection mold. Theproblem with the Kasco method is that the golf balls thus formed havenon-concentric cores. That is, the center of the ball is not concentricwith the remainder of the ball and the layers do not have uniformthickness. More particularly, the first layer was measured to have amaximum thickness on one side of 0.139 inch and a minimum thickness onthe opposing side of 0.106 inch. Thus, there was a variance of 0.033inch in the thickness of the first layer. Similarly, the second layerwas measured to have a maximum thickness of 0.155 on a first side and aminimum thickness of 0.113 inch on the opposing side. Therefore, therewas a difference of 0.042 inch in the thickness of the second layer.Thus it is evident that there is a significant concentricity problem inthese golf balls.

SUMMARY OF THE INVENTION

The present invention is directed to an improved golf ball having a corecomprised of a center and multiple core layers to improve the playingcharacteristics of the golf ball. More particularly, the inventioncomprises a golf ball having a core and a cover in which the core iscomprised of a center and at least one core layer and preferablymulti-core layers surrounding the center. The center is preferablycomprised of a thermoset composition such as high cis or transpolybutadiene or may comprise a thermoset or thermoplastic metallocenesuch as polybutadiene, polyethylene copolymer. The core layers maycomprise the same materials as the center or different compositions.

At least one core layer should be significantly stiffer and harder thanthe innermost core. At least one layer has a Shore C hardness of greaterthan 80 and preferably greater than 90 with a flex modulus of greaterthan about 30,000 psi.

At least one outermost core layer has a specific gravity of greater than1.25 g/cc, preferably greater than 1.50 g/cc, and most preferablygreater than 1.75 g/cc therein increasing the moment of inertia of theoverall golf ball and thereby lowering the spin rates. This outermostcore layer may be heavily filled with density increasing material whilethe center and any intermediate core layers may be filled with a densityreducing material, preferably greater than 2 g/cc, more preferablygreater than 5 g/cc and most preferably greater than 10 g/cc.

Optionally, one or more core layers, most preferably the outermost corelayer, serve as moisture barrier layers to reduce the penetration ofmoisture into the center, which reduces COR values over time.

The invention provides for a single core layer to serve all the abovefunctions: stiffness greater than the center; high specific gravity awayfrom the center; and a barrier to penetrating moisture.

The cover comprises one or more layers of soft material that supplieshigh partial wedge spin and good durability. This material can be a castor reaction-injection molded polyurethane, polyurea,polyurethane-ionomer or a thermoplastic such as a thermoplasticurethane, partially or fully neutralized ionomer, metallocene or othersingle site catalyzed polymer, or blends thereof. The cover willpreferably have a Shore D hardness of less than 65 and a thickness offrom about 0.010 to 0.100 inches, more preferably from 0.020 to 0.040inches. Preferably, the cover comprises a single layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a golf ball formed according to thepresent invention having a single outer core layer.

FIG. 2 is a cross-sectional view of a golf ball formed according to thepresent invention showing three outer core layers.

FIG. 3 is a perspective view of a laminate comprising three layers ofcore material.

FIG. 4 is a sectional view of rollers and material being formed into thelaminate of core material.

FIG. 5 is a sectional view of a mold for forming multiple layers about acore center according to the present invention.

FIG. 6 is a sectional view of a mold forming multiple layers about acore center according to the invention with the mold-forming sheetsbeing vacuum formed within the mold.

FIG. 7 is a perspective view of a half mold used in forming multiplelayers about core centers in accordance with the present invention.

FIG. 8 is a cross-sectional view of a compression mold of a golf ballcore according to the present invention.

FIG. 9 is an exploded view of a golf ball core according to the presentinvention in a retractable-pin injection mold.

FIG. 10 is a cross-sectional view of a golf ball core according to thepresent invention in a retractable-pin injection mold.

FIG. 11 is a cross-sectional view of a golf ball according to thepresent invention in a retractable-pin mold.

FIG. 12 is an exploded view of a golf ball core according to the presentinvention with cover layer hemispheres in a compression mold.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, golf balls 10 include a core 16 and a cover15. Core 16 includes a center 11, and at least one core layer. FIG. 1depicts an embodiment of the invention having just an outer core layer14. However, FIG. 2 describes an embodiment having three thin laminatelayers: a first layer, herein referred to as the innermost core layer12; a second layer, herein referred to as the intermediate layer 13; anda third layer, herein referred to as the outermost core layer 14.

Referring to FIG. 2, the center 11 is preferably formed by compressionmolding a sphere from a prep of center material. Compression moldingsolid centers is well known in the art.

Referring to FIGS. 3 and 4, in order to form multiple layers around thecenter in a first embodiment of the invention, preferably a laminate 20is formed. The laminate 20 is comprised of at least two layers andpreferably three layers 22, 23 and 24. The laminate 20 is formed fromthe rolling of thin sheets 32, 33, and 34 from a core material. Moreparticularly, each sheet is formed to a thickness that is slightlylarger than the thickness of the layers 12, 13 and 14 in the finishedgolf ball 10. The thickness of each may be varied, but all have athickness preferably of about 0.010 to 0.100 inches and more preferablyfrom about 0.010 to 0.050 inches thick.

Preferably, the sheets 32, 33, 34 are prepared by mixing the uncuredcore material to be used for each layer and calendar rolling thematerial into sheets. The sheets are stacked together to form thelaminate 20 having three layers 22, 23 and 24 using calendar rollingmills. The sheets could also be made by extrusion. The sheets 32, 33 and34 should have very uniform thickness i.e. the thickness of each sheetshould not vary more than about 0.005 inch.

In an alternate embodiment, the laminate 20 can be further constructedusing an adhesive between each layer of material. Preferably, an epoxyresin such as Epoxy Resin #1028 from RBC Industries in Warwick, R.I. isused. The adhesive should have good shear and tensile strength and,preferably the adhesive should have a tensile strength over about 1500psi. Still further, the adhesive should not become brittle when cured.An adhesive having a Shore D hardness of less than 60 when cured ispreferred. The adhesive layer applied to the sheets should be very thinand preferably, less than about 0.004 inch thick.

Referring to FIGS. 5 through 8, the next step in the method of thepresent invention is to form multiple layers around the center. This ispreferably accomplished by placing the two laminates 20 and 21 inbetween a top mold 36 and a bottom mold 37. The molds 36 and 37 arecomprised of mold frames 38 and replaceable mold halves 39 such as thatdescribed in U.S. Pat. No. 4,508,309 issued to Brown. The laminates 20and 21 are formed to the cavities in the mold halves 39. Preferably, thelaminates are suction formed by using a vacuum source 40. The vacuumsource 40 suction forms the laminates 20 and 21 to the half moldcavities 39 so that uniformity in layer thickness is maintained. Centers11 are inserted between the laminates after the laminates 20 and 21 havebeen formed to the cavities and the laminates 20 and 21 are compressionmolded about the centers 11 under conditions of temperature and,pressure that are well known in the art.

Referring to FIGS. 7 and 8, the half molds 39 have a plurality of vents41. The compression molding step includes flowing excess layer materialfrom the laminates 20 and 21 through at least three vents 41 so that theflow of laminate material is symmetrical about the center 11 and thecenter 11 does not shift due to lateral flow patterns. Preferably, thehalf molds 39 have 4 to 6 vents.

Referring to FIGS. 9 through 12, the next step in the present inventionis to form a cover 15 around the core 16. The core 16, comprised ofcenter 11 and outer layers 12, 13 and 14, is supported within a pair ofcover mold-halves 50 and 51 by a plurality of retractable pins 52. Theretractable pins 52 are actuated by conventional means well known tothose of ordinary skill in the art of mold design.

After the mold-halves 50 and 51 are closed together with the pins 52supporting the core 16, the cover material is injected into the mold ina liquid state through a plurality of injection ports or gates 49. Gates49 can be edge gates or sub-gates. With edge gates, the resultant golfballs are all interconnected and may be removed from the mold-halves 50and 51 together in a large matrix. Sub-gating automatically separatesthe mold runner from the golf balls during the ejection of the golfballs from mold-halves 50 and 51.

Referring to FIGS. 10 and 11, retractable pins 52 are retracted after apredetermined amount of cover material has been injected into themold-halves 50 and 51. The predetermined amount of cover material issubstantially all of the material to be injected. Thus, the core 16 issubstantially surrounded by cover material and does not shift when theretractable pins 52 are removed. This allows the liquid cover materialto flow and substantially fill the cavity between the core 16 and themold-halves 50 and 51. At the same time, concentricity is maintainedbetween the core 16 and the mold-halves 50 and 51.

The cover material is allowed to solidify around the core 16, therebyforming cover 15. Golf ball 10 is then ejected from mold-halves 50 and51, and finished using processes which are well known in the art. Thetemperatures and curing time for mold-halves 50 and 51 are generallyknown in the art and are dependent on the material that is being usedfor cover 15, which will be discussed in more detail below.

Referring to FIG. 12, an alternative method of forming the cover 15according to the invention is shown. Two cover layer hemispheres 55 and56 are pre-formed of the desired cover material, preferably, by aninjection molding process. The hemispheres 55 and 56 are positionedaround core 16 thereby forming an assembly 57 that is then placed into acompression mold 58, which comprises two compression mold-halves 53 and54. Mold-halves 53 and 54 are advanced toward each other until theirmating surfaces touch, and the mold 58 is heated to melt thehemispheres. Mold-halves 53 and 54 compress and heat the hemispheres 55and 56 about the core 16 to mold the cover material thereto.

Referring back to FIGS. 1-2, the core 16 comprises a center 11 and atleast one outermost core layer 14. The embodiment disclosed in FIG. 2shows the core 16 having intermediate layer 13 and innermost core layer12 in addition to the outermost core layer 14. The overall diameter ofthe core 16 is greater than about 1.50 inches, preferably greater than1.58 inches and most preferably greater than about 1.60 inches. Thecenter 11 has a Shore C surface hardness of less than about 80,preferably less than about 70. The center 11 has a compression of lessthan about 70, preferably less than about 60 and most preferably lessthan about 50, and additionally has a COR value greater than about 0.700and preferably greater than about 0.750. Compression is measured byapplying a spring-loaded force to the golf ball center, golf ball coreor the golf ball to be examined, with a manual instrument (an “Attigauge”) manufactured by the Atti Engineering Company of Union City, N.J.This machine, equipped with a Federal Dial Gauge, Model D81-C, employs acalibrated spring under a known load. The sphere to be tested is forceda distance of 0.2 inch against this spring. If the spring, in turn,compresses 0.2 inch, the compression is rated at 100; if the springcompresses 0.1 inch, the compression value is rated as 0. Thus morecompressible, softer materials will have a lower Atti gauge values thanharder, less compressible materials. Compression measured with thisinstrument is also referred to as PGA compression. The center 11 may bea thermoset composition such as high cis or trans polybutadiene or maymay comprise a thermoset or thermoplastic metallocene (or other singlesite catalyzed polyolefin) such as a polybutadiene, polyethylenecopolymer, or EPR or EPDM. In the case of metallocenes, the polymer maybe cross-linked with a free radical source such as peroxide or byhigh-energy radiation. It is highly desirable that the center 11 be softand fast. The diameter of the center 11 is not critical but since a thinouter core layer(s) is desirable it should be greater than about 1.00inch and may be much higher, up to an outer diameter of about 1.62inches. The enclosing one or more core layers, 13-14, may comprise thesame materials as disclosed above for the center 11, or differentcompositions than the innermost core layer, but at least one core layermust be significantly stiffer and harder than the center 11. At leastone layer 12-14 has a Shore C hardness of greater than 80 and preferablygreater than 90 with a flex modulus (per ASTM D-790) of greater thanabout 30,000 psi. Additionally, at least one core layer, 12-14, has aspecific gravity of greater than 1.25 g/cc, preferably greater than 1.50g/cc and most preferably greater than 1.75 g/cc. This will increase themoment of inertia of the overall ball, and subsequently lower spin rateswhen a driver golf club is used. This may be coupled with the use ofunfilled or even foamed density reducing material to reduce specificgravity of the center 11 and any inner core laminate layers 12-13 tofurther increase the moment of inertia of the ball. Each outer corelayer 12-14 has a thickness of from 0.001 to 0.100 inches and preferablyfrom about 0.010 to 0.050 inches. Optionally, one or more layers 12-14may serve as moisture barrier layers that will protect against reducedCOR values, due to moisture take-up by the center 11. The use ofmoisture barriers is described in co-pending patent application Ser. No.09/973,342, which is incorporated by reference herein in its entirety.FIG. 1 further describes an embodiment of the invention wherein a singlelayer 14 serves one or more of the functions described above, i.e.stiffness, high specific gravity, and moisture barrier. Morespecifically, one or more layers 12-14 having a moisture vaportransmission rate that is less than that of the cover.

The cover 12 comprises one or more layers of a relatively soft materialthat supplies high partial spin to the ball when struck by a wedge club.Preferably, the cover comprises a single layer. The cover 12 should havegood durability as provided by cast polyurethane, polyurea, polyurethaneionomer, or a thermoplastic such as a thermoplastic urethane, ionomerblend, fusabond, etc. It should have a Shore D hardness or less than 65and preferably have a thickness of from about 0.010 to 0.100 inches,more preferably from about 0.020 to 0.040 inches. While multi-layeredcovers may be employed to fine tune spin and feel, the present inventiondoes not require them to provide optimal performance.

In accordance with a preferred embodiment of the present invention(herein referred to as example 1 as shown in FIG. 1), the center 11 hasa diameter of 1.60 inches, a shore C hardness of 60, a compression of 50and a COR of 0.800. It also has a specific gravity of about 1.1 g/cc.Center 11 is enclosed by a single outermost core layer 14, having aShore C hardness of 80 or greater, a thickness of 0.020 inches, and atungsten filler such that the core layer 14 will have a specific gravityof greater than 1.3 g/cc. The cover 15 is of a material such as castpolyurethane and having a hardness of less than 65D and a thickness of0.020 inches. The overall ball 10 has a COR value of greater than 0.790,preferably greater than 0.800 and a compression of less than 100,preferably less than 90. The outermost core layer 14 can function as amoisture barrier. It has a moisture vapor transmission rate less thanthat of the cover layer and more preferably less than the moisture vaportransmission rate of an ionomer resin such as Surlyn®, which is in therange of about 0.45 to about 0.95 grams per mm/m² per day. The moisturevapor transmission rate is defined as: the mass of moisture vapor thatdiffuses into a material of a given thickness per unit area per unittime. The preferred standards of measuring the moisture vaportransmission rate include: ASTM F1249-90 entitled “Standard Test Methodfor Water Vapor Transmission Rate Through Plastic Film and SheetingUsing a Modulated Infrared Sensor,” and ASTM F372-99 entitled “StandardTest Method for Water Vapor Transmission Rate of Flexible BarrierMaterials Using an Infrared Detection Technique,” among others.

In another embodiment (herein referred to as example 2 as shown in FIG.2), the center 11 is the same as in example 1 with the exception thatthe size of its diameter is about 1.50 inches in stead of about 1.60inches. Center 11 is enclosed with three thin laminate layers, aninnermost core layer 13 that functions as a moisture barrier and havinga thickness of about 0.010 inches and a specific gravity of about 1.00g/cc. The intermediate layer 14 has a Shore C hardness of 90 or greater,a thickness of about 0.030 inches and a specific gravity of about 1.00g/cc. The outermost core layer 14 has a thickness of about 0.025 inches,and a specific gravity of about 1.50 g/cc. The cover 15 has a hardnessof less than about 60D and a thickness of about 0.025 inches.

In yet another embodiment, the golf ball 10 is the same as in example 2above, except that the specific gravity of the center 11 is less than1.10 g/cc and may be about 0.90 g/cc, with the specific gravity of theouter most core layer 14.

The above three examples are an improvement over the golf ballconstructions of either U.S. patent application Ser. No. 09/948,692 orU.S. application Ser. No. 09/815,753. The manipulation of moment ofinertia via the filling (or foaming or otherwise reducing specificgravity) of the center 11 and inner laminate layers 12-14 provide theopportunity to further improve upon distance and spin. The low specificgravity center 11 or layers 12 or 13 can be made from a number ofsuitable materials, so long as the low specific gravity contributes tothe soft compression and resilience of the golf ball. The material canbe from a thermosetting syntactic foam with hollow sphere fillers ormicrospheres in a polymeric matrix of epoxy, urethane, polyester or anysuitable thermosetting binder, where the cured composition has aspecific gravity less than 1.1 g/cc and preferably less than 1.0 g/cc.Additionally, any number of foamed or otherwise specific gravity reducedthermoplastic or thermosetting polymer compositions may also be usedsuch as metallocene-catalyzed polymers and blends thereof described inU.S. Pat. Nos. 5,824,746 and 6,025,442 which are incorporated byreference herein in their entirety. Further, a thermoset polyurethanecomposition having a specific gravity or less than 1.0 g/cc such as anucleated reaction injection molded or cast polyurethane may be used.Such a composition may result in a gas-filled or cellular solid layer.

As discussed in U.S. Pat. No. 5,971,870, which is incorporated byreference herein in its entirety, fillers may be or are typically in afinely divided form. For example, in a size generally less than about 20mesh, preferably less than about 100 mesh U.S. standard size, except forfibers and flock, which are generally elongated, flock and fiber sizesshould be small enough to facilitate processing. Filler particle sizewill depend upon desired effect, cost, ease of addition, and dustingconsiderations. The filler preferably is selected from the groupconsisting of precipitated hydrated silica, clay, talc, asbestos, glassfibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zincsulfide, lithopone, silicates, silicon carbide, diatomaceous earth,polyvinyl chloride, carbonates, metals, metal alloys, tungsten carbide,metal oxides, metal stearates, particulate carbonaceous materials, microballoons, and combinations thereof. Non-limiting examples of suitablefillers, their densities, and their preferred uses are as follows:

Filler Type Sp. Gr. Comments Precipitated hydrated silica 2.0 1, 2 Clay2.62 1, 2 Talc 2.85 1, 2 Asbestos 2.5 1, 2 Glass fibers 2.55 1, 2 Aramidfibers (KEVLAR ®) 1.44 1, 2 Mica 2.8 1, 2 Calcium metasilicate 2.9 1, 2Barium sulfate 4.6 1, 2 Zinc sulfide 4.1 1, 2 Lithopone 4.2-4.3 1, 2Silicates 2.1 1, 2 Silicon carbide patelets 3.18 1, 2 Silicon carbidewhiskers 3.2 1, 2 Tungsten carbide 15.6 1 Tungsten oxide 5.8 1Diatomaceous earth 2.3 1, 2 Polyvinyl chloride 1.41 1, 2 CarbonatesCalcium carbonate 2.71 1, 2 Magnesium carbonate 2.20 1, 2 Metals andAlloys (powders) Titanium 4.51 1 Tungsten 19.35 1 Aluminum 2.70 1Bismuth 9.78 1 Nickel 8.90 1 Molybdenum 10.2 1 Iron 7.86 1 Steel 7.8-7.91 Lead 11.4 1, 2 Copper 8.94 1 Brass 8.2-8.4 1 Boron 2.34 1 Boroncarbide whiskers 2.52 1, 2 Bronze 8.70-8.74 1 Cobalt 8.92 1 Beryllium1.84 1 Zinc 7.14 1 Tin 7.31 1 Metal Oxides Zinc oxide 5.57 1, 2 Ironoxide 5.1 1, 2 Aluminum oxide 4.0 Titanium oxide 3.9-4.1 1, 2 Magnesiumoxide 3.3-3.5 1, 2 Zirconium oxide 5.73 1, 2 Metal Stearates Zincstearate 1.09 3, 4 Calcium stearate 1.03 3, 4 Barium stearate 1.23 3, 4Lithium stearate 1.01 3, 4 Magnesium stearate 1.03 3, 4 Particulatecarbonaceous materials Graphite 1.5-1.8 1, 2 Carbon black 1.8 1, 2Natural bitumen 1.2-1.4 1, 2 Cotton flock 1.3-1.4 1, 2 Cellulose flock1.15-1.5  1, 2 Leather fiber 1.2-1.4 1, 2 Micro balloons Glass 0.15-1.1 1, 2 Ceramic 0.2-0.7 1, 2 Fly ash 0.6-0.8 1, 2 Coupling Agents AdhesionPromoters Titanates 0.95-1.11 Zirconates 0.92-1.11 Silane 0.95-1.2  1Particularly useful for adjusting density of the inner cover layer. 2Particularly useful for adjusting flex modulus of the inner cover layer.3 Particularly useful for adjusting mold release of the inner coverlayer. 4 Particularly useful for increasing melt flow index of the innercover layer.

The increased hardness of the intermediate core layer 13 in reference tothe innermost core layer 12 and the outermost core layer 14 provides theball 10 with performance characteristics that have been associatedprimarily with dual cover layer golf balls using ionomer inner coverlayers.

Examining a golf ball made with a small center of 1 inch or less andrelatively thick core layers, each having a thickness of greater than0.1 inch, it will be seen that this structure decreases ball initialvelocity and reduces the ball spin rate effects. When impacting a golfball with different clubs within a set, the impact speed and the impactangle are changed. On an average, for a tour professional the impactspeed of a driver is about 110 miles an hour. The average professionalhitting a 5 iron will have an impact speed of about 90 miles an hour andthe wedge impact velocity is less than about 80 miles an hour. Moreover,the force on the golf ball is broken up into two components, the normalforce that is normal to the club face and the tangential force that isparallel to the club face. Since most professionals use a driver havinga loft of about 10 degrees, the tangential force is significantly lessthan the normal force. However, when using a wedge having a loft between48 and 60 degrees, the tangential force becomes very significant. Forexample, experimental data shows that with a clubhead having an impactvelocity of about 95 miles an hour and an angle of 20 degrees, a twopiece ball has a maximum deflection of about 0.151 inches. When hit witha club head at 95 miles an hour and an impact angle of 40 degrees, theball has a maximum deflection of about 0.128 inches or a difference of0.023 inches. Thus, the impact deflection depends significantly on theimpact angle, and by having outer layers of less than 0.1 inch, the spincharacteristics of the ball is altered for different clubs within a setas discussed in more detail below. Golf balls can be made for all typesof golfers, by properly utilizing the hardness and density of thecenter, core layers and cover material. By creating a golf ball corewith relatively thin outer layers that progressively get harder, thespin rate of the ball is surprisingly good for a player that desires ahigh spin rate golf ball. More particularly, when this type of playerhits the ball with a short iron, only the outer layer and cover affectthe spin rate of the ball. By incorporating a very hard core outer layerand a soft cover, the spin rate is maximized for the short iron shotsuch as a wedge having an angle of about 48 to 60 degrees. In order toreduce the spin rate a little for middle iron shots such as a 6 ironhaving a loft of about 32 degrees to make sure that sufficient distanceis obtained, the second layer is softer than the third layer. Similarly,to decrease the spin rate, provide good distance and a good trajectoryfor long irons such as a 3 iron having a loft of about 20 degrees, thefirst layer is softer than the second layer. Finally for a low spin ratewith the driver having a loft of about 8 to 12 degrees, the center ismade very soft.

Table 1 sets forth the contents that can make-up the golf ball core inthe first embodiment. The compositions used to prepare the golf ballcore of this embodiment are all in parts per hundred (pph), based on 100parts of polybutadiene. The fillers used in the compositions of theseexamples are regrind and barium sulfate (BaSO¼). Vulcup 40KE™. and Varox23IXL™, are free radical initiators, and are a—a bis (t-butylperoxy)diisopropylbenzene and 1,1-di(t-butylperoxy) 3,3,5-trimethylcyclohexane, respectively.

TABLE CORE COMPOSITIONS (pph) Layer No. Center 1 2 3 Polybutadiene 100100 100 100 Polywate 325 26 23 18 13 Vulcup 40KE ™ 0.3 .3 .3 .3 Varox231XL ™ 0.6 .5 .5 .5 BaSO.sub.4 31 26 25 25 Zinc Diacrylate 30 32 35 47SR-350 2 2 2 6 Calcium Oxide 3 0 0 0 Zinc Oxide 0 3 6 6

All the ingredients except the peroxides were mixed in a Process LabBrabender mixer to about 180-200.degree. F. Peroxides were added in thesecond stage to the initial mixture, and the resulting mixture wasremoved from the Brabender and blended on a lab mill to insurehomogeneity. After mixing, the mixture was then hand rolled using alaboratory mill and cut into pieces or “preps”. To make the core centers11 the preps were then compression molded at about 160° C. for about 15minutes. To fabricate the outer layers, polybutadiene rubber materialwas rolled into flat sheets and the sheets were stacked to form alaminate. The laminate was then compression molded around the centers asdescribed above. To form the finished golf balls, the cores were groundand inserted into two cover hemispheres of materials that were suitablefor use in a cover layer. These may include any number of partially orfully neutralized ionomers such as those disclosed in the parentapplication, or described in WO 00/23519, WO 01/29129. Also anythermosetting or thermoplastic polyurethanes or polyureas, including anyaliphatic or aromatic polyether or polyester polyurethanes such as butnot limited to those disclosed in U.S. Pat. Nos. 6,309,313; 6,210,294;6,117,024; 5,908,358; 5,929,189; 5,334,673 and U.S. application Ser. No.09/466,434. Additionally, other suitable cover materials are disclosedin U.S. Pat. No. 5,919,100 and also in any of the co-pendingapplications referenced herein.

Referring back to the core layers 12, 13 and 14, these can be made ofthermosetting or thermoplastic materials. For example, the first, secondand third layers 12, 13 and 14 can be formed from thermoplasticelastomers, functionalized styrene-butadiene elastomers, thermoplasticrubbers, thermoset elastomers, thermoplastic urethanes, metallocenepolymers, urethanes, or ionomer resins, or blends thereof.

The thermoplastic elastomers include dynamically vulcanizedthermoplastic elastomers and blends thereof. Suitable dynamicallyvulcanized thermoplastic elastomers include Santoprene®, Sarlink®,Vyram®, Dytron® and Vistaflex®. Santoprene® is the trademark for adynamically vulcanized PP/EPDM. Santoprene® 203-40 is an example of apreferred Santoprene® and is commercially available from AdvancedElastomer Systems.

Examples of suitable functionalized styrene-butadiene elastomers includeKraton FG-1901x and FG-1921x, available from the Shell Corporation.Examples of suitable thermoplastic polyurethanes include Estane® 58133,Estane® 58134 and Estane® 58144, which are available from the B.F.Goodrich Company. Further, the materials for the first, second and thirdlayers 12, 13 and 14 described above may be in the form of a foamedpolymeric material. For example, suitable metallocene polymers includefoams of thermoplastic elastomers based on metallocene single-sitecatalyst-based foams. Such metallocene-based foams are commerciallyavailable from Sentinel Products of Hyannis, Mass.

Suitable thermoplastic polyetheresters include Hytrel® 3078, Hytrel®G3548W, and Hytrel® G4078W which are commercially available from DuPont.Suitable thermoplastic polyetheramides include Pebax® 2533, Pebax® 3533,Pebax® 1205 and Pebax® 4033 which are available from Elf-Atochem.Suitable thermoplastic polyesters include polybutylene terephthalate.

Suitable thermoplastic ionomer resins are obtained by providing a crossmetallic bond to polymers of monoolefin with at least one memberselected from the group consisting of unsaturated mono- or di-carboxylicacids having 3 to 12 carbon atoms and esters thereof. The polymercontains 1 to 50% by weight of the unsaturated mono- or di-carboxylicacid and/or ester thereof. More particularly, low modulus ionomers, suchas acid-containing ethylene copolymer ionomers, include E/X/Y copolymerswhere E is ethylene, X is a softening comonomer such as acrylate ormethacrylate present in 0-50 (preferably 0-25, most preferably 0-2),weight percent of the polymer, and Y is acrylic or methacrylic acidpresent in 5-35 (preferably 10-35, most preferably 15-35, making theionomer a high acid ionomer) weight percent of the polymer, wherein theacid moiety is neutralized 1-100% (preferably at least 40%, mostpreferably at least about 60%) to form an ionomer by a cation such aslithium*, sodium*, potassium, magnesium*, calcium, barium, lead, tin,zinc* or aluminum (*=preferred), or a combination of such cations.Specific acid-containing ethylene copolymers include ethylene/acrylicacid, ethylene/methacrylic acid, ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylicacid/methyl acrylate, ethylene/methacrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl methacrylate, and ethylene/acrylicacid/n-butyl methacrylate. Preferred acid-containing ethylene copolymersinclude ethylene/methacrylic acid, ethylene/acrylic acid,ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

Such ionomer resins include SURLYN®. and lotek®, which are commerciallyavailable from DuPont and Exxon, respectively. Likewise, otherconventional materials such as balata, elastomer and polyethylene mayalso be used in the first, second and third layers 12, 13 and 14 of thepresent invention.

Such thermoplastic blends comprise about 1% to about 99% by weight of afirst thermoplastic and about 99% to about 1% by weight of a secondthermoplastic.

Preferably the thermoplastic blend comprises about 5% to about 95% byweight of a first thermoplastic and about 5% to about 95% by weight of asecond thermoplastic. In a preferred embodiment of the presentinvention, the first thermoplastic material of the blend is adynamically vulcanized thermoplastic elastomer, such as Santoprene®.

The properties such as hardness, Bayshore resilience modulus, centerdiameter and layer thickness of the golf balls of the present inventionhave been found to affect play characteristics such as spin, initialvelocity and feel of golf balls.

The golf ball of the present invention can have an overall diameter ofany size. Although the United States Golf Association (USGA)specifications limit the minimum size of a competition golf ball to morethan 1.680 inches in diameter, there is no specification as to themaximum diameter. Moreover, golf balls of any size can be used forrecreational play. The preferred diameter of the present golf balls isfrom about 1.680 inches to about 1.800 inches. The more preferreddiameter is from about 1.680 inches to about 1.760 inches. The mostpreferred diameter is about 1.680 inches to about 1.740 inches.

While it is apparent that the illustrative embodiments of the inventionherein disclosed fulfill the objectives stated above, it will beappreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. Therefore, it will be understoodthat the appended claims are intended to cover all such modificationsand embodiments which come within the spirit and scope of the presentinvention.

What is claimed is:
 1. A golf ball comprising: a multi-layer corehaving: a center having a Shore C surface hardness of less than about 80and a compression of less than 70, at least one outer core layer havinga Shore C hardness of greater than 80, and a specific gravity of greaterthan 1.25 g/cc; and a cover having a Shore D hardness of less than 65,wherein at least one outer core layer has a moisture vapor transmissionrate that is lower than that of the cover.
 2. The golf ball according toclaim 1, wherein the center has a Shore C hardness of less than
 70. 3.The golf ball according to claim 1, wherein the center has a Shore Chardness of less than
 60. 4. The golf ball according to claim 1, whereinat least one outer core layer has a Shore C hardness of greater than 90.5. The golf ball according to claim 1, wherein at least one outermostcore layer has a specific gravity of greater than 1.30 g/cc.
 6. The golfball according to claim 1, wherein at least one outermost core layer hasa specific gravity of greater than 1.50 g/cc.
 7. The golf ball accordingto claim 1, wherein at least one outermost core layer has a specificgravity of greater than 1.75 g/cc.
 8. The golf ball according to claim1, wherein the center has a specific gravity of less than 1.1 g/cc. 9.The golf ball according to claim 1, wherein the cover has a Shore Dhardness of less than
 60. 10. The golf ball according to claim 1,wherein the multi-layer core has a diameter of from 1.50 inches to 1.66inches.
 11. The golf ball according to claim 1, wherein the centercomprises a first solid polybutadiene rubber and the at least one outercore layer comprising of a second solid polybutadiene rubber material.12. A golf ball comprising: a multi-layer core having: a center having aShore C surface hardness of less than about 80 and a compression of lessthan 70, a diameter from 1.58 inches to 1.66 inches, at least one outercore layer having a Shore C hardness of greater than 80, and a specificgravity of greater than 1.25 g/cc; and a cover having a Shore D hardnessof less than
 65. 13. A golf ball comprising: a multi-layer core having:a center having a Shore C surface hardness of less than about 80 and acompression of less than 70, at least one outer core layer having aShore C hardness of greater than 80, and a specific gravity of greaterthan 1.25 g/cc; at least one cover layer; the at least one cover layerhaving a Shore D hardness of less than 65; and the at least one coverlayer is selected from a cast or reaction-injection moldablethermosetting material.
 14. The golf ball according to claim 13, furthercomprises a second cover layer comprising an ionomer, thermoplasticpolyurethane, polyamide, polyester or a single-site catalyzed polymer.15. The golf ball according to claim 13, wherein the cover comprises asingle layer having a thickness of about 0.010 inches to about 0.090inches.
 16. The golf ball according to claim 13, wherein the covercomprises a single layer having a thickness of about 0.020 inches toabout 0.050 inches.